If there is anything that is an absolute in waterfowling, it is that there are no absolutes! By that I mean on any given day, the birds may want a lot of calling, or very little, but I would never generalize it to a time of year or part of the season. We have had days where the birds wanted screamed at all the way in, and the very next day under the same conditions, we just got their attention then shut up. Reading birds is the key here. Seeing their reaction to the different sounds you make and go with what they like.